1. Field of the Invention
This invention relates to a writing instrument, more particularly to a writing instrument which has a light assembly.
2. Description of the Related Art
Writing under the presence of insufficient light is harmful to the eyes. Even in the presence of an external light source, a dim area is still provided around the writing tip of a conventional writing instrument due to the shadow of the hand which holds the writing instrument.
According to the U.S. Pat. No. 5,275,497, there is disclosed a writing instrument with a light assembly which is operable to provide additional light when writing. The writing instrument includes a conductive barrel, a nib assembly, a thrusting assembly and a lamp assembly. The conductive barrel has an open top end and an open bottom end. The nib assembly includes a hollow nib casing which is transparent and which has an open top end connected to the open bottom end of the barrel and a tapered open bottom end. An ink tube has an upper end and a lower writing tip and is disposed inside the nib casing. A coil spring is sleeved on the ink tube to bias the ink tube inwardly of the barrel. The ink tube is movable between a first position, wherein the writing tip is disposed in the nib casing and a second position, wherein the writing tip extends out of the nib casing through the open bottom end of the latter. The thrusting assembly includes a hollow insulating cap member which has an open bottom end connected to the open top end of the barrel and an open top end. A push-button is provided on the open top end of the cap member and is operable to move the ink tube between the first and second positions. A conductive clip assembly is clamped between the cap member and the open top end of the barrel. A transparent push-member is disposed slidably inside the conductive barrel adjacent to the nib casing and has a lower end which abuts against the upper end of the ink tube. The lamp assembly includes an insulating lamp holder which is disposed slidably inside the barrel above the push-member and which has a lower end abutting against the push-member. The lamp holder retains a lamp therein. The lamp has a first electrode in electrical contact with the barrel and a second electrode. An insulating battery seat is disposed slidably inside the barrel above the lamp holder and has a lower end abutting against the lamp holder. The battery seat receives a battery therein. The battery has a first terminal connected electrically to the second electrode of the lamp and a second terminal. The battery seat further has a first conductive spring connected to the second terminal of the battery so as to bias the battery toward the lamp holder. The thrusting assembly further includes an insulating switch bar which has an upper end extending into the cap member and which is in contact with the lower end of the push-button. The insulating switch bar has a lower end extending into the barrel and is in contact with the battery seat. A conductive member is positioned adjacent to the upper end of the insulating switch bar. A second conductive spring is provided in the insulating switch bar and biases the conductive member to contact the first conductive spring so as to connect electrically the conductive member and the second terminal of the battery. The insulating switch bar is movable between a switch-off condition, wherein the ink tube is in the first position and the conductive member is spaced from the clip member to turn off the lamp, and a switch-on condition, wherein the ink tube is in the second position and the conductive member is in contact with the clip member to turn on the lamp.
In the above-mentioned writing instrument, the lower end portion of the insulating switch bar has an axial blind bore to receive a spring member therein and a pair of split members extending axially and downwardly from the lower end portion to define a receiving slot which is communicated with the axial blind bore. The conductive clip assembly includes a ring member which has a pair of inwardly and radially protrusions. The conductive member employed in the disclosed writing instrument is cylinder-shaped with small diameter and has two opposed radial extensions which project outwardly from a position adjacent to its lower end. When the conductive member is received in the insulating switch bar, an upper portion of the conductive member extends into the axial blind bore of the insulating switch bar while the radial extensions of the conductive member project outwardly from the insulating switch bar via the receiving slot of the same. During the operation of the push-button to move the ink tube into a writing or non-writing position, the conductive member correspondingly moves together downwardly or upwardly with the push-button. The second conductive spring is disposed slidably in the receiving slot of the insulating switch bar without any retaining means. Therefore, the vertically extending position of the second conductive spring is not stable and fails to bias and retain the radial extensions of the conductive member in a horizontally position. This results in misalignment and poor contact of the radial extensions of the conductive member relative to the inwardly and radially protrusions of the clip assembly, thereby resulting in poor electrical contact of the lamp assembly.